For the photoconductive materials to constitute an image-forming member for use in solid image pickup device or electrophotography, or to constitute a photoconductive layer for use in image-reading photosensor, it is required to be highly sensitive, to have a high SN ratio [photocurrent (Ip)/dark current (Id)], to have absorption spectrum characteristics suited for the spectrum characteristics of an electromagnetic wave to be irradiated, to be quickly responsive and to have a desired dark resistance. It is also required to be not harmful to living things as well as man upon the use.
Others than these requirements, it is required to have a property to remove a residual image within a predetermined period of time in solid image pickup device.
Particularly for the image-forming member for use in an electrophotographic machine which is daily used as a business machine at office, causing no pollution is indeed important.
From these standpoints, the public attention has been focused on light receiving members comprising amorphous materials containing silicon atoms (hereinafter referred to as "a-Si"), for example, as disclosed in Offenlegungsschriftes Nos. 2746967 and 2855718 which disclose use of the light receiving member as an image-forming member in electrophotography and in Offenlegungsschrift No. 2933411 which discloses use of the light receiving member in an image-reading photosensor.
For the conventional light receiving members comprising a-Si materials, there have been made improvements in their optical, electric and photoconductive characteristics such as dark resistance, photosensitivity, and photoresponsiveness, use-environmental characteristics, economic stability and durability.
However, there are still left subjects to make further improvements in their characteristics in the synthesis situation in order to make such light receiving member practically usable.
For example, in the case where such conventional light receiving member is used as an image-forming member in electrophotography with aiming at heightening the photosensitivity and dark resistance, there are often observed a residual voltage on the conventional light receiving member upon the use, and when it is repeatedly used for a long period of time, fatigues due to the repeated use will be accumulated to cause the so-called ghost phenomena inviting residual images.
Further, in the preparation of the conventional light receiving member using an a-Si material, hydrogen atoms, halogen atoms such as fluorine atoms or chlorine atoms, elements for controlling the electrical conduction type such as boron atoms or phosphorus atoms, or other kinds of atoms for improving the characteristics are selectively incorporated in a light receiving layer of the light receiving member as the layer constituents.
However, the resulting light receiving layer sometime becomes accompanied with defects on the electrical characteristics, photoconductive characteristics and/or breakdown voltage according to the way of the incorporation of said constituents to be employed.
That is, in the case of using the light receiving member having such light receiving layer, the life of a photocarrier generated in the layer with the irradiation of light is not sufficient, the inhibition of a charge injection from the side of the substrate in a dark layer region is not sufficiently carried out, and image defects likely due to a local breakdown phenomenon which is so-called "white oval marks on half-tone copies" or other image defects likely due to abrasion upon using a blade for the cleaning which is so-called "white line" are likely to appear on the transferred images on a paper sheet.
Further, in the case where the above light receiving member is used in a much moist atmosphere, or in the case where after being placed in that atmosphere it is used, there sometimes appear the so-called "image flow" on the transferred images on a paper sheet.
Further in addition, in the case of forming a light receiving layer of a ten and some m.mu. in thickness on an appropriate substrate to obtain a light receiving member, the resulting light receiving layer is likely to invite undesired phenomena such as a thinner inbetween space being formed between the bottom face and the surface of the substrate, the layer being removed from the substrate and a crack being generated within the layer following the lapse of time after the light receiving member is taken out from the vacuum deposition chamber.
These phenomena are apt to occur in the case of using a cylindrical substrate to be usually used in the field of electrophotography.
In consequence, it is necessitated not only to make a further improvement in an a-Si material itself but also to establish such a light receiving member not to invite any of the foregoing problems.